Baroness Thatcher used her training as a chemist to approach politics 'with the mindset of a scientist', her longtime friend Dame Mary Archer said today.

The wife of former Conservative Party chairman Lord Jeffrey Archer believes Lady Thatcher's early career as a scientist was key to understanding her time as prime minister.

She told the Daily Telegraph: 'Her approach was evidence-based, a wish to understand things thoroughly, never to skate over the surface.

Admirer: Dame Mary Archer (seen here with Baroness Thatcher at a Tory Party conference in 1999) said the former prime minister tackled politics with the 'mindset of a scientist'

Scientist: Margaret Thatcher working as a young chemist in 1950 when was part of a team which helped develop the first soft-serve ice cream

'Many distinguished politicians would go on gut and instinct, which isn't the scientific way.

'To borrow a phrase from Al Gore, as a scientist she was prepared to accept inconvenient truths if the evidence demanded it.'

Dame Mary, who also has a chemistry degree, shared her passion for science with Lady Thatcher when the Archers began an annual ritual in 1991 of hosting the former prime minister and her husband, Denis, at their home in Grantchester for a weekend.

On one occasion, she invited Nobel Prize-winning scientist Sir John Sulston to give a talk on his work on the human genome project, while another time she organised a tour of Addenbrooke's Hospital in Cambridge to see a surgery training centre.

Close friends: Lady Thatcher with Mary and Jeffrey Archer at the couple's silver wedding celebrations in 1991

Dame Mary also discovered by chance that they shared the same chemistry teacher, albeit 20 years apart and at different schools.

Lady Thatcher won a scholarship to the Kesteven and Grantham Girls’ School and became a gifted scientist there before, in October 1943, winning a place at Somerville College, Oxford, where she studied chemistry.

Seven years later, she got a research job at food manufacturer J. Lyons and Co, where she was part of a team which helped develop the first soft-serve ice cream.

Fan: Lady Thatcher appointed Lord Archer deputy chairman of the Tories in 1985 and backed him in his abandoned bid to become London's first mayor

She later changed her career path after she was called to the bar before going into politics.

The relationship between Lady Thatcher and Lord Archer had gone back even further. She had appointed him deputy chairman of the Tories in 1985 and backed him in his abandoned bid to become London's first mayor.

The Thatchers also attended the Archers' silver wedding anniversary.

Dame Mary will be accompanying Lord Archer for Lady Thatcher's funeral at St Paul's on Wednesday.